The invention relates to an electric disconnect or grounding switch having a switch blade movable about a fulcrum into a stationary blade contact having a slot open on one side.
Disconnect switches of the above type are generally known. See, for example, British Pat. No. 1,406,173, particularly FIGS. 12 to 15 thereof. In the open condition of the disconnect or grounding switch, the movable switch blade is approximately parallel to the stationary blade contact, and the fulcrum about which the switch blade is moved is located above or below the region of the current contacts of the blade contact. Rotation of the switch blade when the switch is being closed moves the free end of the switch blade toward the blade contact and into the central slot thereof through the open end of the central slot. Rotation continues until the switch blade reaches the switch end position in the vicinity of the current contacts of the blade contact and comes to rest in a position perpendicular to the blade contact. Because of the position of the switch blade relative to the blade contact, forces are generated when current flows through the switch which urge the switch blade out of the blade contact. The blade contact is also open adjacent the current contacts thereof between which the blade contact comes to rest. Since the blade contact is open at the end adjacent the contacts, it offers little resistance, namely, only the friction of the free end current contacts, to the switch blade. As a result, it is possible, particularly in the event of a short circuit, that the forces generated by the current flow exceed the friction forces of the current contacts resiliently urged against the switch blade and force the switch blade out of the blade contact. For this reason, external locking devices are sometimes provided.